Gas turbine engines such as aero engines are required to generate electrical energy for various purposes within and external to the engine, such as to provide power for control systems or to provide electrical power to an airframe. In currently machines, an electrical generator that supplies electrical power required by the gas turbine engine is driven by a mechanical gearbox. The electrical generator and the mechanical gearbox are mounted within the nacelle of the engine. Current power requirements have caused the size of the electrical generator is increasing to meet the increasing power demands of aircraft. For gas turbine engines that are wing- or fuselage-mounted, the increased size of the electrical generator may require enlarging the nacelle, resulting in increased aircraft drag.
One system provides an electrical machine that operates as a generator or motor, incorporated in a gas turbine engine. The compressor blades may be shrouded at the radially outer end to separate the aerodynamic part of the blades from the electrical rotor projection. Beyond the shroud, an electrical machine is provided by rotor projections attached to the compressor blade. The projections run in a channel of flux cores resulting in an electrical machine, which is external to the combustion gas paths of the engine, for ready access, with optimized magnetic flux paths. The shroud of the blades forms a ring around the outer periphery of the gas path for containment of gases, the shroud having seals between the shroud and the walls of the channel to resist gas leakage around the shroud and into the channel.
Another system provides a mechanical link from a rotating component of the engine to a generator in order to generate enough electrical power to meet the increased demands. Another system, in an attempt to reduce the level of mechanical complexity in the mechanical linkage system, incorporates an electrical generator within the rotating spools of the engine, preferably the high-pressure spool. However, space limitations in the region of the central axis of the engine have been found to be such that this proposal is not wholly satisfactory.
Likewise, another gas turbine engine includes an electrical generator. The generator can also be operated as a motor to provide drive, such as for starting the engine. The engine includes at least one ring of rotating blades. The motor/generator is formed from a rotating part comprising the rotating blade ring, and a fixed part comprising a plurality of coils arranged circumferentially around the blade ring. While this method reduces the complexity of the machine construction, it relies on traditional methods and system for excitation of the fan blades.
Therefore, what is needed is a method and system to utilize gas turbine fan or compressor blades as poles for an integrated electric machine for increased aircraft engine electric power generation within the existing nacelle, while providing a transverse flux electric machine suited to the structure of the fan or compressor blade tips for the excitation of the system.